1. Field
Aspects of the present invention relate to a busbar for electrically connecting a plurality of cells of a battery module. The invention also relates to a battery module including such a busbar as well as to a vehicle including such a battery module and a method for construction of a busbar.
2. Description of the Related Art
A rechargeable battery differs from a primary battery in that it can be repeatedly charged and discharged, while a primary battery makes only an irreversible conversion of chemical energy to electrical energy. Low-capacity rechargeable batteries are used as the power supply for small electronic devices, such as cellular phones, notebook computers and camcorders, while high-capacity rechargeable batteries are used as the power supply for driving motors in hybrid vehicles and the like.
In general, rechargeable batteries include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, a case receiving the electrode assembly, and an electrode terminal electrically connected to the electrode assembly. The case may have a cylindrical or rectangular shape depending on the purpose and the usage of the rechargeable battery, and electrolyte solution is injected into the case for charging and discharging of the rechargeable battery through an electrochemical reaction of the positive electrode, the negative electrode, and the electrolyte solution.
Rechargeable batteries may be used as a battery module formed of a plurality of unit batteries or cells coupled in series so as to be used to power a motor driving a hybrid vehicle that benefits from high energy density. For example, the battery module may be formed by connecting an electrode terminal of each of the plurality of unit batteries depending on the amount of power required for motor driving, such that a high-power rechargeable battery can be realized. The cells of the battery module usually are connected by a so-called “busbar”, sometimes also called a “bussbar” or a “bus bar”. Busbars are usually monolithic and made out of solid metal, because their primary (or sometimes only) function is to electrically connect the cells of the battery module with each other to transfer electrical currents between cells of the battery module.
In order to improve the safety of the battery module, heat generated from the rechargeable battery may be efficiently emitted, discharged and/or dissipated. If the heat emission/discharge/dissipation is not sufficiently performed, a temperature deviation may occur between the respective unit batteries, such that the battery module cannot generate a desired amount of power for motor driving. In addition, if the internal temperature of the battery increases due to the heat generated from the rechargeable battery, an abnormal reaction occurs therein and thus charging and discharging performance of the rechargeable deteriorates and the life-span of the rechargeable battery is shortened. Thus, a cooling device that can cool the rechargeable battery by effectively emitting/discharging/dissipating heat generated from the battery can improve the safety, performance, and life-span of the rechargeable battery.
In case of failure of the heat dissipater or the cooling device, respectively, or due to another malfunction in one of the battery cells, for example an internal short circuit, thermal runaway of a cell can occur. Due to the busbar being monolithic and made of solid metal, which conducts heat at a high rate, heat is transferred to the neighboring cells of the battery module. It is desirable to reduce, minimize, or eliminate this effect, because overheating and thus failure of the cells can occur, leading to complete failure and possibly the destruction of the battery module.
Further, in case of an internal short circuit in the battery system, e.g. due to deformation of the battery system during an impact or an accident, the monolithic metal busbar maintains the short circuit current. Hence, heat dissipation continues, possibly affecting other cells of the battery modules or other components of the vehicle or of the device which the battery module is part of.